Airflow/circulating design for one-row heat exchanger

ABSTRACT

In a single row evaporator coil having a last tube receiving refrigerant in a superheated condition, at least one baffle is provided to divert the flow of air passing over the superheat tube such that it also passes over a nonsuperheat tube so that air can be dehumidified by the cooling effect of the nonsuperheat tube prior to the air being passed downstream.

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to air conditioning systems and,more particularly to an evaporator coil having a single row of tubes.

[0002] An evaporator coil is ordinarily made up of a plurality ofsections, with each section having two or more rows of tubes. The tubesare commonly interconnected at their ends by return bends such that oneor more circuits are formed with a plurality of interconnected tubessuch that, with the introduction of refrigerant into a first tube, therefrigerant flows successively through the tubes until it reaches a lasttube, after which the refrigerant flow then passes out of the coil andis made to flow to the compressor.

[0003] An air conditioning system is so designed that the refrigerantpassing into successive tubes gets progressively evaporated, and when itreaches the last tube, it is in a superheated vapor condition. Thepurpose of this is to protect the compressor by preventing any liquidrefrigerant from passing to the compressor.

[0004] It is recognized that superheat tubes can potentially be abovethe air dew point temperature. Accordingly, humid air passing over thesuperheat tube is not dehumidified as is the air passing over the othernon superheated tubes. If nondehumidified air is allowed to pass throughthe heat exchanger, it may cause a fogging effect downstream thereof.That is, as the high humidity air mixes with cold air downstream, fogcan be generated, or condensation can form on cold surfaces. The resultmay be that fog and/or water is then blown into the conditioned space.With a coil of two or more rows, this problem is overcome by the factthat the air passing over the superheat tube has passed or will passover a nonsuperheated tube from another row. Thus the air passing overthe superheated tube is dehumidified by a nonsuperheated tube, and thefogging problem is averted.

[0005] For purposes of reducing cost and weight, it would be desirableto replace a multi-row, low fin density coil with a single row, high findensity coil. However, since there is no adjacent unsuperheated tube todehumidify the air passing over the superheated tube, the problem of foggeneration is present.

[0006] It is therefore an object of the present invention to provide animproved single row coil.

[0007] Another object of the present invention is the provision forovercoming the problem of fogging in a single row coil.

[0008] Yet another object of the present invention is the provision forreducing the flow of non-dehumidified air from a single row coil.

[0009] Still another object of the present invention is the provisionfor a single row coil which is economical to manufacture and effectiveand efficient in use.

[0010] These objects and other features and advantages become readilyapparent upon reference to the following descriptions when taken inconjunction with the appended drawings.

SUMMARY OF THE INVENTION

[0011] Briefly, in accordance with one aspect of the invention,provision is made in a single row coil for the air flow to be divertedin such a way that the air being cooled and passing over a superheattube in the circuit is also made to pass over a nonsuperheat tube suchthat the air is dehumidified prior to its passing downstream of thecoil.

[0012] By yet another aspect of the invention, at least one baffle isplaced near the heat exchanger superheat tube such that the incoming airflow is diverted to obtain the desired dehumidifying effect.

[0013] By yet another aspect of the invention, a pair of baffles areprovided in the vicinity of the superheat tube, with one on each side ofthe tube row, and with the two being staggered such that the desired airflow diversion is obtained.

[0014] By still another object of the present invention, the diversionof air can be such that the air passes first over the superheat tube andthen over a nonsuperheat tube or first over a nonsuperheat tube and thenover a superheat tube.

[0015] In the drawings as hereinafter described, a preferred embodimentis depicted; however, various others modifications and alternateconstructions can be made thereto without departing from the true spritand scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a schematic illustration of a conventional two-row coilsystem with the pattern of air flow shown.

[0017]FIG. 2 shows a schematic illustration of a one-row coil system.

[0018]FIG. 3 is a schematic illustration of a one-row coil system withthe present invention incorporated therein.

[0019]FIG. 4 is a schematic illustration of an alternative form of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] Referring now to FIG. 1, a two-row coil system is shown withthree sections 11, 12 and 13, with each section having two rows of tubesas shown. Within each section, refrigerant is caused to flow betweensuccessive tubes, with the refrigerant quality progressively increasing(i.e. evaporating) in each tube. That is, as the fan 14 draws airthrough the sections as indicated by the arrows, the air is cooled bythe cooler refrigerant in the tubes, and conversely the refrigerant isheated by the air. The system is designed such that the temperature ofthe two-phase refrigerant in the tubes is below the air dew pointtemperature in most of the tubes, but when it reaches the last tube inthe section, the temperature of the refrigerant vapor is typically abovethe air dew point temperature. These last tubes are referred to assuperheat tubes and are indicated by the number 16, 17 and 18 in therespective sections 11, 12 and 13.

[0021] The purpose of the superheat tubes is to ensure that therefrigerant passing to the compressor is in a superheated stage and notin a liquid or two-phase stage since the compressor may be damaged byliquid refrigerant. However, it is recognized that the cooling abilityof the superheat tube is different from the nonsuperheat tubes in thecoil. That is, when the warm humid air enters the coil, the nonsuperheattubes have sufficient cooling capacity to also dehumidify the airpassing through, whereas the superheat tubes, typically being above theair dew point temperature, are not capable of dehumidifying the air.Because of the two-row structure, this is not a problem since the airpassing across the superheat tubes is previously passed over thenonsuperheat tubes where the air is dehumidified. The result is that allof the air passing downstream of the fan 14 is cold dry air.

[0022] Considering now a coil with sections 19, 21 and 22 having asingle row of tubes as shown in FIG. 2, it should be pointed out thatthere are only two circuits in the three sections, with one circuitstarting in section 19 and ending in section 21, and with the othercircuit starting in section 21 and ending in section 22. Here, theproblem of having nondehumidified air can occur. That is, each of thenonsuperheat tubes 23 are sufficiently cool as to be capable ofdehumidifying the air passing through the coil. But the superheat tubes24 and 26 can, again, be above the air dew point temperature andtherefore not capable of dehumidifying the air. Further, unlike in thetwo coil arrangement as described hereinabove, the air passing over thesuperheat tubes 24 and 26 does not pass over any of the nonsuperheattubes 23. As a result, the air passing over the superheat tubes 24 and26 is humid air which, when mixed with cold air downstream, can causethe generation of fog or the formation of condensate on cold surfaces.This can, in turn, cause fog or water to be blown into the conditionedspace. This problem is addressed by the inventive arrangement as shownin FIG. 3.

[0023] In order to dehumidify the air passing over the superheat tubes24 and 26 the air flow is diverted by a pair of baffles 27 and 28 insection 21 and baffles 29 and 31 in section 22. As will be seen, thebaffle pairs are staggered in respect to their respective superheattubes such that the air flow is redirected from the superheated tubes toan adjacent two phase tube to thereby further cool the air and therebydehumidify it. This eliminates the previously described problem of fogand condensate formation caused by the mixing of cold, dry air withwarmer humid air.

[0024] As an alternative to the above arrangement, wherein the air to becooled flows first over the superheat tube 26 and then over the twophase tube, the baffles can be rearranged as shown at 32 and 33 of FIG.4 wherein the air passes first over the two phase tube 34 and then overthe superheat tube 26.

[0025] While the present invention has been particularly shown anddescribed with reference to a preferred and an alternative mode asillustrated in the drawings, it will be understood by one skilled in theart that various changes in detail may be effected therein withoutdeparting from the spirit and scope of the invention as defined by theclaims.

We claim:
 1. An evaporator coil having a plurality of tubes andassociated fins for the heat exchange flow of air thereover the coilcomprising: a single row only of tubes with adjacent tubes beinginterconnected at their ends by a return bend to form at least oneserpentine circuit for conducting the flow of refrigerant from a firsttube to a last tube, with the quality of the refrigerant progressivelyincreasing and the temperature of the refrigerant in said last tubebeing superheated; and at least one baffle associated with said lasttube for diverting the flow of air such that a substantial portion ofthe air passing over said last tube also passes over another tube.
 2. Anevaporator coil as set forth in claim 1 wherein said baffle is so placedthat the flow of air passes first over said last tube and then over saidother tube.
 3. An evaporator coil as set forth in claim 1 wherein saidbaffle is so placed that the air passes first over said other tube andthen over said last tube.
 4. An evaporator coil as set forth in claim 1wherein said at least one baffle includes two baffles.
 5. An evaporatorcoil as set forth in claim 4 wherein said two baffles are planar in formand are aligned substantially parallel to said tube row, with one oneither side thereof.
 6. A method of fabricating an evaporator coilhaving only a single row of tubes over which a flow of air to be cooledmay pass, comprising the steps of: constructing a refrigeration circuitwith a plurality of tubes arranged in a row with adjacent tubes beinginterconnected by a return bend; providing a means for introducing theflow of refrigerant in said tubes such that it flows from a first tubeto a last tube; and providing at least one baffle to divert the flow ofair to be cooled such that a substantial portion of the air passing oversaid last tube also passes over another tube.
 7. A method as set forthin claim 6 wherein said baffle providing step includes that of providingtwo baffles with one on each side of said tube row.
 8. A method as setforth in claim 6 wherein said baffle is so placed as to cause said airto pass first over said last tube and then over said other tube.
 9. Amethod as set forth in claim 6 wherein said baffle is so placed as tocause said air flow to pass first over said other tube and then oversaid last tube.
 10. A method as set forth in claim 7 wherein saidbaffles are placed in staggered relationship with one on each side ofsaid tube row.